Normally, a user terminal that receives a mail from an electronic mail server sets a time interval for sending an electronic mail to and receiving an electronic mail from a user using the terminal in order to suppress increasing of traffic, sends a receipt requirement of newly received electronic mails to the electronic mail server at the interval, and receives electronic mails from the electronic mail server. In this case, the user using the terminal cannot recognize the newly received electronic mails until the electronic mail server and the user terminal communicate with each other next time. The time interval is various with respect to each user. A user of which number of received mail is small may set the time interval to 30 minutes to one hour. On the other hand, a user of which number of received mail is large may set the time interval to a few minutes. Therefore, there is variability among the time intervals of users.
Japanese Patent Application Publication No. 10-313338 discloses a technology in which a user sets a condition with respect to an electronic mail server in advance, the electronic mail servers informs the user terminal of arriving of an electronic mail when the electronic mail server receives an electronic mail having a condition corresponding to the condition.